The Centers for Advanced Orthopaedics
Maryland Orthopedic Specialists
A Division of The Centers for Advanced Orthopaedics
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Knee

Patellar Fracture

A patellar fracture is a break in the kneecap — the triangular bone at the front of the knee that serves as the mechanical fulcrum of the extensor mechanism. While some patellar fractures can be managed without surgery, fractures that disrupt the extensor mechanism or involve significant displacement require operative fixation to restore the ability to straighten the knee. Maryland Orthopedic Specialists provides prompt evaluation and expert fixation for all types of patellar fractures.

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What is patellar fracture?

A patellar fracture is a break in the kneecap, the bone at the front of the knee that transmits the force of the quadriceps muscle to the shinbone. It usually results from a direct blow or fall. Symptoms include pain, swelling, and difficulty straightening or lifting the leg.

The patella transmits extensor forces from the quadriceps to the patellar tendon and tibial tubercle. Fractures occur by two principal mechanisms:

  • Direct blow — a fall directly onto the kneecap (the most common mechanism); often produces comminuted or stellate fracture patterns
  • Forceful quadriceps contraction — the pulling force of the quadriceps on the superior patella and patellar tendon on the inferior patella creates tension that can split the patella transversely; produces transverse fractures, which are the most common pattern overall

Fracture classification by pattern:

  • Transverse: Most common (50–80%); horizontal split through mid-patella
  • Stellate / Comminuted: Multiple fragments from direct blow; extensor mechanism often intact
  • Polar (Superior / Inferior): Avulsion of patellar pole from tendon attachment
  • Vertical: Uncommon; rarely disrupts extensor mechanism
  • Osteochondral: Articular surface shear; seen with patellar dislocation

The critical clinical distinction is whether the extensor mechanism is intact or disrupted — this, not fracture displacement alone, dictates surgical versus non-operative management.

Frequently Asked Questions

Why might I need surgery if I can still somewhat move my knee?
Extensor mechanism integrity is tested by a straight-leg raise against gravity, not by partial range of motion. Patients with partial extensor tears may still lift the leg. Surgery is indicated when there is a measurable gap, step-off, or any extensor lag, as untreated displacement leads to post-traumatic arthritis.
Will my hardware need to come out?
Patellar hardware — particularly tension band wires — is symptomatic enough to require removal in approximately 30–50% of patients. Your surgeon will discuss a planned removal procedure once your fracture has fully healed.
How long will recovery take after a patellar fracture?
Recovery time varies depending on whether the fracture was treated non-surgically or surgically. Non-surgical treatment with a brace or cast typically requires four to six weeks of immobilization, followed by a graduated physical therapy program, with most patients returning to full activity by three to four months. After surgical fixation, weight-bearing often begins earlier with the knee in extension, but regaining full strength and range of motion can take four to six months. High-demand athletes may require six to twelve months before returning to competitive sport.
What are the long-term risks after a patellar fracture?
The most common long-term concern is post-traumatic arthritis of the patellofemoral joint, since the kneecap cartilage may be damaged at the time of injury even when the fracture heals well. Other potential issues include loss of full knee flexion (stiffness), weakness of the quadriceps, and, in cases treated with hardware, hardware-related irritation that may eventually require removal. Your MOS surgeon will monitor your recovery and address any complications promptly to maximize your long-term knee function.
Will I be able to return to sports or strenuous activity after a patellar fracture?
Most patients do return to recreational and even competitive sports after a patellar fracture, provided the fracture heals well and rehabilitation is completed fully. The key milestones for return to sport include achieving near-symmetric quadriceps strength, full or near-full range of motion, and pain-free activity-specific movements. At MOS we use functional testing alongside your subjective readiness to clear patients for sport, rather than relying solely on a fixed time frame.

Meet the specialists

Christopher S. Raffo, MD

Christopher S. Raffo, MD

Orthopedic Surgery · Sports Medicine

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John J. Christoforetti, MD

John J. Christoforetti, MD

Orthopedic Surgery · Sports Medicine · Hip Preservation Surgery

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James S. Gardiner, MD

James S. Gardiner, MD

Orthopedic Surgery · Sports Medicine

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Related conditions

Patellar Instability / DislocationQuadriceps Tendon Rupture
Medically reviewed by Christopher S. Raffo, MD
Last reviewed May 1, 2026

References

  1. Bostrom A. "Fracture of the patella: a study of 422 patellar fractures." Acta Orthopaedica Scandinavica Supplementum. 1972;143:1–80. PMID:4197175
  2. Lazaro LE, Wellman DS, Sauro G, et al. "Outcomes after operative fixation of complete articular patellar fractures: assessment of functional impairment." Journal of Bone and Joint Surgery (American). 2013;95(14):e96(1–8). doi:10.2106/JBJS.L.00521
  3. Wild M, Eichler C, Thelen S, Jungbluth P, Windolf J, Hakimi M. "Fixed-angle plate osteosynthesis of the patella: an alternative to tension banding." International Orthopaedics. 2010;34(4):577–581. doi:10.1007/s00264-009-0802-0
  4. OrthoInfo — AAOS. "Patellar Fracture (Kneecap Fracture)." American Academy of Orthopaedic Surgeons. https://orthoinfo.aaos.org/en/diseases--conditions/patellar-fractures-kneecap-fractures